Motion blur on texture
Motion blur will not work because the object doesn't move in the scene. What you need to do is to blur the texture in the nodes. For it there is nice node group named ImageBlur from the b°wide NodePack. This node will blur the image in all directions, put it between Tex. Coords. and Image Texture nodes. You can control the amount of blur:



To blur only in one direction we need to adjust the ImageBlur group node. Add those Separate RGB, Add and Combine RGB nodes and change marked values:



Now you have blur only in one direction:



If you also plug in 2 Mapping nodes with opposite values for rotation in Z you can change the blur angle: